TESTING
TREATMENTS - BETTER RESEARCH
FOR
BETTER HEALTHCARE
- CHAPTER III - Excerpt
KEY
CONCEPTS IN FAIR TESTS OF TREATMENTS
In the early
1990s, a team of researchers in the USA looked in medical textbooks and
journals to identify the recommendations for the treatment of heart
attacks made over a period of 30 years.45 They then compared these
recommendations with the evidence that could have been taken into
account had the results of fair tests been reviewed systematically. The
researchers found that, because the authors of the textbooks had not
bothered to reduce the misleading effects of bias and the play of
chance when they reviewed the evidence, there were serious consequences
for
patients. In some cases patients had been deprived of reliable advice
on life-saving therapies (for example, clot-busting drugs for heart
attacks), sometimes for more than a decade; in others, doctors had
continued to recommend treatments long after fair tests had shown they
were harmful (for example, anti-arrhythmic drugs in heart attack – see
Chapter 1).
Researchers who do not review past tests of treatments before embarking
on new studies may not realise that uncertainties about treatment
effects have already been convincingly addressed. This means that some
patients are taking part in research unnecessarily and being denied
treatment
that can help them. For example, long after there was reliable evidence
that giving antibiotics to patients having bowel surgery reduced their
chances of dying from complications of the operation, researchers
continued to do comparison studies that involved withholding antibiotics
from half the patients participating in the studies (see Chapter 5).
Conversely, sometimes when previous results are reviewed it soon
becomes apparent that reliable evidence is lacking – so new studies are
definitely needed.
And, as we pointed out in Chapter 1 (page 9), patients can also suffer
when researchers have not reviewed relevant evidence from animal
research systematically before beginning to test treatments in
patients. In that example, had the results of animal experiments been
reviewed,
clinical trials of the drug nimodipine in stroke patients would never
have been done.
The idea of reviewing evidence systematically is far from new. The
subtitle of James Lind’s 1753 Treatise of the Scurvy, in which he
reported his fair test of then favoured remedies (see Chapter 1),
indicates that it contains ‘A critical and chronological view of what
has been published on
the subject’.
AVOIDING BIASED
COMPARISONS
To ensure that comparisons are fair, several sources of bias must be
identified and minimised; if they are not, a new treatment might appear
better than an existing one when in fact it is not.
In considering individual research studies, this could result from:
- comparing
the progress of relatively well patients given a new treatment with the progress of
relatively ill patients given a standard treatment
- biased
assessment of the results of treatment – for example, by comparing the opinions of patients or
doctors who know that they have used an expensive new treatment, and who think this
is better, with
the opinions of those who know that they have had an existing standard treatment
And in
reviewing several similar studies, from:
- considering
only studies that show a new treatment in a favourable light, without including other
‘negative’ studies that have either failed to confirm it has benefits, or suggest
that it may be harmful (‘negative’ studies are often not reported)
- biased
selection from and interpretation of the available evidence.
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